linux-kernel - Re: [PATCH 1/1] lib/test_vmalloc: do not create cpumask

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Date:   Thu, 18 Apr 2019 15:10:33 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     "Uladzislau Rezki (Sony)" <urezki@...il.com>
Cc:     Roman Gushchin <guro@...com>, Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Garnier <thgarnie@...gle.com>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joelaf@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...e.hu>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH 1/1] lib/test_vmalloc: do not create cpumask_t variable
 on stack

On Thu, 18 Apr 2019 21:39:25 +0200 "Uladzislau Rezki (Sony)" <urezki@...il.com> wrote:

> On my "Intel(R) Xeon(R) W-2135 CPU @ 3.70GHz" system(12 CPUs)
> i get the warning from the compiler about frame size:
> 
> <snip>
> warning: the frame size of 1096 bytes is larger than 1024 bytes
> [-Wframe-larger-than=]
> <snip>
> 
> the size of cpumask_t depends on number of CPUs, therefore just
> make use of cpumask_of() in set_cpus_allowed_ptr() as a second
> argument.
> 
> ...
L
> --- a/lib/test_vmalloc.c
> +++ b/lib/test_vmalloc.c
> @@ -383,14 +383,14 @@ static void shuffle_array(int *arr, int n)
>  static int test_func(void *private)
>  {
>  	struct test_driver *t = private;
> -	cpumask_t newmask = CPU_MASK_NONE;
>  	int random_array[ARRAY_SIZE(test_case_array)];
>  	int index, i, j, ret;
>  	ktime_t kt;
>  	u64 delta;
>  
> -	cpumask_set_cpu(t->cpu, &newmask);
> -	set_cpus_allowed_ptr(current, &newmask);
> +	ret = set_cpus_allowed_ptr(current, cpumask_of(t->cpu));
> +	if (ret < 0)
> +		pr_err("Failed to set affinity to %d CPU\n", t->cpu);
>  
>  	for (i = 0; i < ARRAY_SIZE(test_case_array); i++)
>  		random_array[i] = i;

lgtm.

While we're in there...


From: Andrew Morton <akpm@...ux-foundation.org>
Subject: lib/test_vmalloc.c:test_func(): eliminate local `ret'

Local 'ret' is unneeded and was poorly named: the variable `ret' generally
means the "the value which this function will return".

Cc: Roman Gushchin <guro@...com>
Cc: Uladzislau Rezki <urezki@...il.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Thomas Garnier <thgarnie@...gle.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Joel Fernandes <joelaf@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Tejun Heo <tj@...nel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 lib/test_vmalloc.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

--- a/lib/test_vmalloc.c~a
+++ a/lib/test_vmalloc.c
@@ -384,12 +384,11 @@ static int test_func(void *private)
 {
 	struct test_driver *t = private;
 	int random_array[ARRAY_SIZE(test_case_array)];
-	int index, i, j, ret;
+	int index, i, j;
 	ktime_t kt;
 	u64 delta;
 
-	ret = set_cpus_allowed_ptr(current, cpumask_of(t->cpu));
-	if (ret < 0)
+	if (set_cpus_allowed_ptr(current, cpumask_of(t->cpu)) < 0)
 		pr_err("Failed to set affinity to %d CPU\n", t->cpu);
 
 	for (i = 0; i < ARRAY_SIZE(test_case_array); i++)
@@ -415,8 +414,7 @@ static int test_func(void *private)
 
 		kt = ktime_get();
 		for (j = 0; j < test_repeat_count; j++) {
-			ret = test_case_array[index].test_func();
-			if (!ret)
+			if (!test_case_array[index].test_func())
 				per_cpu_test_data[t->cpu][index].test_passed++;
 			else
 				per_cpu_test_data[t->cpu][index].test_failed++;
_